Sequence of activation of template biosyntheses in normal and transformed human cells after synchronization with a double thimidine block

The sequences of synthesis of DNA, RNA, and various groups of proteins in normal and transformed human fibroblasts was studied in the first mitotic cycle synchronization of the cells by a double thymidine block. Two peculiarities of the synthesis of acid-soluble histone and acid-insoluble proteins in the normal and transformed cells, were detected: (1) in normal fibroblasts the synthesis of the two groups of proteins is a minimum before DNA replication, and the greatest activity is achieved in the G/sub 2/ phase; in transformed cells protein synthesis is a maximum after the removal of the thymine block, while in the G/sub 2/ phase it is decreased; (2) in normal fibroblasts the synthesis of acid-insoluble proteins is a maximum before the maximum synthesis of DNA, and that of acid-soluble proteins is a maximum after the maximum of DNA synthesis. The opposite picture is observed in transformed cells. RNA synthesis in normal and transformed cells is activated at the end of the G/sub 2/ phase. In normal cells the synthesis of proteins is coupled with the activation of RNA synthesis, while in transformed cells protein synthesis is evidently transferred to the following mitotic cycle. Especially pronounced differences were detected in the expressionmore » of certain LMG proteins. Thus, in transformed cells the regulation of the coupling of the template syntheses is modified.« less